Widening of the diploic space

Widening of diploic space refers to expansion of the spongy or cancellous bone between the inner and outer tables of the calavarium. The diploic space is the medullary cavity of the skull, and a location of normal physiologic hematopoiesis in adults. Thus, expansion of this structure most commonly occurs in the setting of chronically increased intramedullary hematopoiesis. The widened appearance is most commonly bilateral.

Causes

Most commonly caused by systemic underlying pathologies such as:

• chronic haemolytic disorders: may be associated with vertical striations running in diploic space giving rise to the characteristic hair on end sign
• • sickle cell disease
  • thalassaemia
  • iron deficiency anaemia
  • and other chronic severe anaemias
• metabolic disorders
  • renal osteodystrophy
  • hyperparathyroidism
• overgrowth
  • microcephaly
  • acromegaly
• medication
  • phenytoin